The Morphology Core has been extensively restructured in response to the concerns of the reviewers of the original application. The overall goal of the facility remains to enable visualization of the spatial relationships between both cellular and subcellular components of the GI tract by providing technical services, consultation, and training in morphological approaches at the light and electron microscope levels of resolution. A major objective is to provide all DDRCC members with services for embedding and sectioning of GI tissues in a timely manner and at low cost. The facility is under the expert direction of Drs. Rubin (director) and Lorenz (co-director), both of whom have extensive experience in GI morphology and in a variety of specialized morphological techniques. This represents a change from the original application, in which Dr. Kevin Roth (current director of the Molecular Biology and Pharmacology Morphology Core) was sole director of this Facility. The resource consists of three components: histology, confocal microscopy, and electron microscopy. It is anticipated that histology will be the most heavily subscribed component of the Core, with 27 projected users. Histological services (paraffin-embedding and sectioning, special stains, preparation of cryosections) will be provided at a new site located in the Division of Gastroenterology, immediately adjacent to Dr. Rubin's laboratory and near the laboratories of many DDRCC members. This change is believed to be the best way to ensure quality control over the service. This site is currently well-equipped for histology and light microscopy, so an extensive start-up budget will not be required. Because the current and projected use of confocal microscopy and electron microscopy is relatively low (nine and 12 projected users, respectively), a separate site will not be maintained for these services. Arrangements have been made to enable DDRCC members to use the Confocal Imaging facility and Electron Microscopy facility (administered by Dr. Robert Wilkinson and Marilyn Levy, respectively) in the Department of Cell Biology and Physiology at a reduced cost (subsidized by DDRCC funds). Dr. John Heuser, Professor of Cell Biology and Physiology and a leading expert in imaging techniques, and Dr. Kevin Roth who is the director of the Molecular Biology and Pharmacology Morphology Core will serve as consultants for the DDRCC Facility.